“In politics, as in life, you can’t keep on doing something that doesn’t work. You can’t keep repeating the same mistakes.”

Mr Clegg explained: “If you were waging any other war where you have 2,000 fatalities a year, your enemies are making billions in profits, constantly throwing new weapons at you and targeting more young people — you’d have to say you are losing and it’s time to do something different.

“I’m anti-drugs — it’s for that reason I’m pro reform.”

Clegg's comments came after Prime Minister David Cameron ignored the findings of a parliamentary inquiry that suggested the UK needed a royal commission to consider reforms — including the possibility of legalization. The Sun reports that the difference of opinion between the two had led to a "behind-the-scenes bust-up" with Cameron.

Clegg is leader of the Liberal Democrats, long the third party in the UK's two party system. After a brief period of "Cleggmania", the party was swept into a coalition government with Cameron's Conservative party in 2010. However, many believe the party has failed to make its mark and it has suffered in opinion polls ever since.